From D&D Wiki

You touch a beast that has died within the last 24 hours, and that creature returns to life with 1 hit point. This spell can't return to life a beast that has died of old age, cannot restore missing body parts, and has no effect on a creature other than a beast with a Challenge Rating (or level) of 2 or lower.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, you can increase the Challenge Rating of the beast this can affect by 2 for each spell slot level above 4th.